Multi camera render addon issue
I downloaded and "installed from file" this script in 2.79:

https://raw.githubusercontent.com/lapineige/Blender_add-ons/master/Multi-Camera-Render/multi_camera_render_v2-1.py

Then, selected both (2) cameras and pressed the "multiple camera render" and it produced 2 images, as expected. 



With the addon default settings (empty directory) those images were created in the blender folder itself (I use a zip blender version); selecting a folder on my desktop as "directory" they were created in that folder, as expected...